Mining0 pages

Pumping challenges in the mining process
Mining
Mining is a tough, uncompromising
process and the mining industry is equally
demanding being driven by the goals of
mine profitability, plant efficiency, cost
minimisation and yield maximisation.
¡ Ores have varying mineral contents and recovery systems
must accommodate such variations. Pumps must consistently
vary their dosing rates to optimise chemical usage and
maintain plant throughput. Peristaltic pumps have a linear
flow-speed characteristic and excellent repeatability, an
ideal complement to plant SCADA systems.
¡ Process reagents, such as cyanides and acids are often
highly corrosive but as the chemically resistive hose is the
only part in contact with the pumped product then there are
no working parts exposed to the chemical.
¡ Many process chemicals, including Powder Activated
Carbon (PAC), are highly abrasive, creating continual wear
problems for progressing cavity pumps leading to ongoing
high stator replacement costs and frequent maintenance
downtime.
¡ pH moderating chemicals, such as lime, are usually too
abrasive for diaphragm pumps, causing them to persistently
clog up, resulting in continual downtime and maintenance
requirements. Verderflex peristaltic pumps have an
exceptional record dosing lime into process and waste,
many being used for bulk dosing to remediate post-mining
waste and effluents.
¡ Reagents may be mixed at the mine or the processing
plant leading to less than perfectly dissolved solutions
but such solids in the liquid stream are not a problem for
a Verderflex peristaltic pump - mine operators can use
pumping solutions that allow for mining realities.
¡ The seal-free design of the Verderflex peristaltic pump
eliminates leaks and the consequent risk of workplace or
environmental contamination.
¡ For aggressive activator solutions including Copper
Sulphate, pumps can optionally be fully Nickel plated to
maximise corrosion resistance and prolong the pump’s
operational life.
¡ Flocculants and coagulants can be highly shear sensitive
products, where excessive shearing noticeably affects
plant performance. Verderflex peristaltic pumps have a
gentle pumping action which result in a low shear rate.
Mining industry studies have shown that Verderflex hose
pumps maintain flocculent particle size. The same studies
showed that progressive cavity pumps reduced particle
sizes by approximately 50 to 75%, reducing flocculation
performance thereby increasing chemical usage to
maintain throughputs or requiring longer flocculation times.
Dosing Process Reagents, Coagulants and
Flocculants
Thickener Underflow
¡ Mining slurries often have sub-micron solid contents in excess
of 80% by weight and have slurry specific gravities (SGs) in
excess of 2.0 - Usually these slurries are also highly abrasive.
A Verderflex peristaltic pump is ideal for slurries of this type.
¡ In addition to their abrasion resistant slurry pumping
performance, hose pumps can be reversed to clear thickener
blockages if necessary.
¡ Peristaltic pumps have a smooth liquid passage, there is no
opportunity for the product to settle as the peristaltic action
keeps the product in suspension.
¡ The Verderflex VF125, with a 125mm or 5” internal diameter
hose, is the world’s largest high pressure hose pump
with single pump slurry flow rates in excess of 60m3/hour.
This allows larger high SG thickeners to be designed,
maximising process plant yields.
Benefits of using a Verderflex® Peristaltic Pump
to pump slurries
¡ Traditional low cost solutions such as centrifugal pumps
can suffer from severe impeller wear requiring frequent
replacement. This brings consequent downtime and high
maintenance costs which are often measured in days -
A False Economy!
¡ Attempts to increase maintenance intervals, with such
traditional solutions often use expensive wear-resistant alloys,
often installing the more costly parts once the pump is in
service.
¡ A Verderflex hose pump, is by definition, rubber-lined and
does not suffer abrasive wear – the lifetime of it’s only service
part, the hose, is primarily related to pump speed.
¡ Alternative solutions using rotary lobe pumps rely on
consistent close tolerances between the rotor and casing
to maintain performance and similarly, require extensive
maintenance.
At a South African mine, gold is
recovered using the heap leaching
process - abandoned spoil heaps
or tailings are treated with cyanide
to separate out the residual gold.
Typically, these early 1900s workings
still contain around 2% gold
and the heap leaching process
recovers over 99% of the residual
gold.
Three VF25 pumps are used to dose
the treatment chemical, cyanide,
throughout the recovery process.
Firstly, cyanide is dosed onto the
spoil heap to dissolve the residual
gold, leaching it from the sand and
then the initial leachate is treated
again with cyanide to increase the
reclamation percentage.
The Verderflex range is particularly
useful for this application because
of its sealless pump design (preventing
liquid spills), the ability to
pump solids (allowing for imperfect
reagent mixing), dosing
consistency and a hose which is
chemically resistant to hazardous
treatment compounds.
Dosing heap
leaching reagents
A mine in the Peruvian Andes has
to dose sodium chromate, sodium
cyanide, copper sulphate and xanthate.
They have installed five Verderflex
pumps (two VF25s, one VF15 and
two VF10s) because of their
excellent repeatablity and accurate
dosing as well as their ability
to handle corrosive media.
Reagent Dosing
Plant must -
¡ Perform as expected
¡ Have a low cost of ownership
¡ Be reliable, be easy to maintain and not require
specialist maintenance skills
¡ Be able to survive the rigours of the mining environment
¡ Be resistant to operator induced problems
Mining pumps should -
¡ Deliver repeatable quantities of products into the
process, stabilising process variables
¡ Have high levels of plant availability
¡ Resist abrasive wear
¡ Withstand normal pumped product or process variations
¡ Be controllable via plant control systems
¡ Be easy to maintain yet require infrequent attention
¡ Not affect overall levels of plant performance